HEIDENHAIN iTNC 530 (340 422) ISO programming - Manual (Page 205)

HEIDENHAIN iTNC 530 205
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Calculating the radius-compensated path in
advance (LOOK AHEAD): M120
Standard behavior
If the tool radius is larger than the contour step that is to be machined
with radius compensation, the TNC interrupts program run and
generates an error message. M97 (see “Machining small contour
steps: M97” on page 201) can be used to prohibit the error message,
but this will result in dwell marks and will also move the corner.
If the programmed contour contains undercut features, the tool may
damage the contour.
Behavior with M120
The TNC checks radius-compensated paths for contour undercuts and
tool path intersections, and calculates the tool path in advance from
the current block. Areas of the contour that might be damaged by the
tool are not machined (dark areas in figure at right). You can also use
M120 to calculate the radius compensation for digitized data or data
created on an external programming system. This means that
deviations from the theoretical tool radius can be compensated.
Use LA (Look Ahead) after M120 to define the number of blocks
(maximum: 99) that you want the TNC to calculate in advance. Note
that the larger the number of blocks you choose, the higher the block
processing time will be.
Input
If you enter M120 in a positioning block, the TNC continues the dialog
for this block by asking you the number of blocks LA that are to be
calculated in advance.
Effect
M120 must be located in an NC block that also contains radius
compensation G41 or G42. M120 is then effective from this block until
n radius compensation is canceled, or
n
M120 LA0 is programmed, or
n M120 is programmed without LA, or
n Call another program with %...
M120 becomes effective at the start of block.
Limitations
n After an external or internal stop, you can only re-enter the contour
with the function RESTORE POS. AT N.
n If you are using the path functions G25 and G24, the blocks before
and after G25 or CHF must contain only coordinates of the working
plane.
X
Y